Nursing Care and Fever Mechanism
Fever/Febrile Response
Fever is an abnormally high body temperature that occurs as part of a host response to pyrogens (fever producers). An alternate term for fever is pyrexia, with hyperpyrexia referring to high fever. It is misleading to define fever simply in terms of temperature elevation, however, because it emphasizes only the thermal manifestations of the nonspecific systemic host defense called the acute phase response (APR).
APR is triggered by endogenous nous release of
cytokines, including interleukin-1 (IL-1), IL-6, and tumor necrosis factor
(TNF), that cause a cascade of biochemical events, autonomic reactions, and
immune responses including heat generation. Some promote immune stimulant
properties against infectious disease and tumors.
How Hypothalamus Play Its Part
Pyrogens readjust hypothalamic regulatory centers to a higher set-point range, so that body temperature is maintained at higher levels. In true fever, other cytokines, hormones, and endogenously produced bio-chemicals act as cryogens with antipyretic properties that limit temperature elevation in fever.
Controlled temperature elevation and intact thermoregulatory function differentiate fever from hyperthermia, a potentially lethal condition in which unregulated thermoregulatory function can produce neurologically damaging high temperatures.
Fever occurs in three phases, reflecting rise and fall of circulating pyrogens. Initially, the chill phase occurs when thermostatic mechanisms are activated to raise body temperature to the newly elevated set point range. Vasoconstriction decreases skin perfusion, conserving heat but making skin feel cold.
Shivering generates heat and is stimulated by sensory
inputs that detect discrepancies between existing temperatures and the new set
point. The plateau phase follows when body temperature rises to the new set
point and warming responses cease. Finally, falling pyrogen levels lead to the
deferve scence phase, with diaphoresis and vasodilation.
Nursing Aspects of Fever
Nurses have managed fever throughout history, yet the scientific evidence supporting care decisions is relatively recent. The lag between basic research findings and clinical application is evident in the reluctance of many nurses to change methods of care that have been used for the past century.
Early traditions of cooling febrile patients were empirically based on the limited state of scientific knowledge and the erroneous fear that elevated body temperature was the cause, rather than the result, of febrile illness. Intervention was therefore geared toward lowering body temperature.
Current knowledge confirms that fever is the host's response to illness or invasion, cooling the body is counterproductive, distressful to patients, and may cause compensatory overwarming.
Febrile symptom Reducing Temperature Reducing
Evidence of fever's host benefits led investigators to focus on methods to reduce distressful febrile symptoms rather than reducing temperature.
F ebrile shivering is among the most distressful and energy consuming symptoms of fever, particularly in immunosuppressed patients with opportunistic infections or those receiving antigenic drugs or blood products.
Vigorous shivering is sometimes described by patients as "bone shaking." Nonpharmacologic nursing interventions are based primarily on thermoregulatory dynamics to:
(a) Insulate thermosensitive areas of skin from cooling to reduce shivering
(b) Facilitate heat loss from less thermosensitive regions without chilling.
(c) Restore fluid volume and improve capillary blood flow to skin.
Fear of neural damage due to protein denaturation during high fevers is justified at temperatures over 42° C. However, true fevers are usually self-limiting and remain well below this level. Body temperatures of about 39 C may have added immuno stimulant and antimicrobial effects.
These features make comfort the primary reason for treating low-grade fever with antipyretic drugs. Higher set point levels raise sensitivity to heat loss, causing even mild cooling to stimulate shivering. Aggressive cooling with conductive cooling blankets and ice packs evokes vigorous shivering, raising energy expenditure 3 to 5 times resting values.
As the consistent clinical
observer of patient body temperatures, nurses find that issues of measurement,
febrile patterns, physiological correlates, and sensory responses are of
significance to practice and research (see Thermal Balance).
Symptoms Related to Fever
Febrile symptoms are nonspecific responses to both infectious and host defense activities so that many symptoms and interventions are generalizable.
Contrasted with studies of fever management in other disciplines that center primarily on pharmacologic control of underlying infection, nursing research focuses on symptom management of fever responses regardless of etiology.
Nurse researchers began studying interventions in the early 1970s to cool the body during fever without causing shivering or temperature "drift." By the late 1980s, concern grew about metabolic and cardiorespiratory effects of fever on vulnerable patients with cancer or HIV infection (Holtzclaw, 1998).
The "set point" theory of temperature regulation was central to these intervention studies, but as discoveries of the 1990s identified and clarified mechanisms of endogenous pyrogens, cytokines and other biological messengers offered new measurable biomarkers of fever as a host response.
Nurse scientists
contributed significant scientific information about the febrile response using
human and animal models (McCarthy, D., Murray, Galagan, Gern, & Hutson,
1998; Richmond, 2002; Rowsey & Gordon, 2000).
Sub Cellular and Molecular Changes In Fever
Responsible nursing research on fever draws on principles from physiology, physics, biochemistry, and psychoneuroimmunology. It is often interdisciplinary and diverse in nature, varying from laboratory studies of humans and animals to clinical studies in hospitals and homes.
Circadian variations in temperature are well-documented (Bailey & Heitkemper, 2001), but there are few recent studies that confirm that daily temperature screening in hospitals adequately detects fever in persons with abnormal cytokine expression, such as those with HIV/AIDS.
A study of febrile symptom management in patients with cancer tested interventions to sup press drug-induced febrile shivering (Holtz-claw, 1990) showed that insulating thermo-sensitive skin regions during the chill phase of fever not only reduced shivering (see shivering) but improved comfort.
This preliminary work provided the basis for a comprehensive febrile-symptoms management protocol, tested in hospitalized and home-care HIV-infected persons with febrile illness (Holtzclaw, 1998). In a controlled trial, the intervention of insulative coverings to suppress shivering was shown to be effective.
Water Loss By Fever and Its Measurement By Body Weight
Body water loss and dehydration were monitored by body weight, serum osmolality, and urine specific gravity in hospitalized patients, while a fever diary and home visits reported changes in patients at home.
No patients with insulative wraps shivered, while controls experienced both shivering and higher peak temperatures. Systematic oral fluid replacement was not effective in replacing loss despite metabolic, cardiorespiratory, and fever related fluid expenditures, because fever suppressed thirst.
Findings documented the negative effects of fever on hydration and febrile shivering on cardiorespiratory effort. Higher fatigue levels, lower thermal comfort, higher rate pressure product (RPP) and respiratory rate (RR) were experienced by those in the control group who shivered.
A growing awareness that cooling measures exert distressful and sometimes harmful effects has stimulated inquiry surrounding procedures commonly used to "cool" patients.
The practice of sponge bathing with tepid water to cool down febrile (38.9 C) children was studied in a group of 20 children, ages 5 to 68 months, seen in an emergency room and randomly assigned to acetaminophen alone or acetaminophen with sponge bathing (Sharber , 1997).
Cool Blanket Vs Sponge Bath and Acetaminophen
Although the sponge-bathed children cooled faster during the 1st hour, rapid cooling evoked higher distress and no significant temperature difference between groups over the 2-hour study period.
There is evidence that a gradual, less drastic reduction in body temperature evokes fewer adverse responses during aggressive fever treatment with cooling blankets. Warmer settings effectively lower body temperature as well as cooler levels, without inducing shivering (Caruso, Hadley, Shukla, Frame, & Khoury, 1992).
Two
studies demonstrate that in comparisons of sponge baths, hypothermia cooling
blankets, and acetaminophen (Morgan, S., 1990) and of cooling blankets vs.
acetaminophen (Henker et al., 2001), no temperature lowering advantage was seen
in the physical cooling treatment, which required more nursing time, caused
shivering, and was distressful.
Nursing Research and Fever Care
Today's nurse scientist is prepared to investigate many of the questions that remain unanswered in fever care. As investigators acquire skills and resources for these biological measurements, they can be used to quantify and qualify the effects of fever and results of intervention.
Research is needed to demonstrate effects of elevated body temperature, cooling interventions, and measures to support natural temperature stabilizing mechanisms. Fever may provide study variables, with body temperature, cytokines, and biochemical correlates being the outcome of interest.
The febrile episode itself may be the context of other questions for study. Psycho neuroimmunology factors surrounding sleep, irritability, and tolerance of febrile symptoms remain untapped topics.
Likewise, the metabolic toll of fever on nutritional variables, effects of
intravenous fluid on endogenous anti pyresis, and measures of energy expenditure
are important, but relatively untouched, areas of research for nursing.
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